Deleting Users Best Practices

I searched the forums for something on this, but came up dry. Running WPMU 2.9.1 with BuddyPress 1.2, I am wondering where I should be adding/administering/deleting users. There is the Site Admin > Users area where one can add/delete users, and also the Users > Add Users area. I have noticed that deleting users from the Users area does not immediately delete them from the Site Admin area. As such, I have deleted a couple of test users twice. Is there a recommended practice for this sort of thing?